Porous silicon is a light emitting material that can emit visible light. In its natural state, it is highly resistive., i.e. insulative, and its open structure allows doping of foreign element(s) into porous silicon. Although it has a strong luminescence, its spectrum is broad and therefore not suitable for potential light emitting device application. Doping can change the optical property of porous silicon, producing a narrower bandwidth luminescence spectrum and better color tuning over the visible waveband. There are several doping methods that can be used: co-deposition, ion-implantation, and electro-chemical deposition. The first method is difficult to achieve due to the incompatibility between the fabrication solution and the doping solution.
The second method (ion-implantation) can only be applied to a small area and implantation time is a function of doping depth. In fact, implantation time can be as long as 3 hours or more.
The third method, however, can be used to apply to a large area in a shorter time and compatible existing semiconductor chip processing. With appropriate lithographic masking, light emitting or optoelectronic integrated devices can be produced on a wafer.